I have spent quite a few hours searching Google for ideas ... and hardware-wise I think it's relatively simple (e.g. Pi 3 + HifiBerry + speakers). It is the software side of things that I am struggling with.
While on holiday recently, we were spoilt with the use of a Sonos system. We all enjoyed adding our individual Apple Music accounts and adding music to the queue. As a family we have both iPhones and Android phones and the Sonos app was available for both and it worked great (although we did have a few discussions over using "play later" rather than "play now"!).
So, is there a software solution, for the Pi, that gives the same sort of functionality? The ability to send music to one or multiple or different speakers? The ability to control / add music from a phone app (I guess a web page would be a possible alternative). The ability for multiple people to add to the same queue?
Of course, free would be great, but I wouldn't mind having to spend some money to get a really good solution.